1. Field of the Invention
The present invention relates to an association method for associating a communication management apparatus, a bandwidth allocation management apparatus, a relay apparatus, and a wireless terminal with each other, and, relates to the relay apparatus, the communication management apparatus and the bandwidth allocation management apparatus.
2. Description of the Related Art
In VoIP (Voice Over IP) communications in a wireless LAN environment, voice data is transmitted between a relay apparatus and a wireless apparatus at predetermined periodic intervals. In the communications, there is a possibility that delay occurs in the voice data when another wireless terminal starts to transmit a large amount of data. Therefore, it is required to be able to prioritize specific communication data such as voice data when a plurality of communications are performed.
There are following methods, for example, for performing control (to be referred to as “priority control” hereinafter) for sending/receiving specific communication packets preferentially in a wireless LAN.
Japanese Laid-Open Patent Application No. 2005-229591 (to be referred to as Patent Document 1) discloses a communication system in which identifying information of wireless terminals are stored in a SIP server, and the SIP server records communication states of wireless terminals so as to restrict the number of calls at the same access point to preserve bandwidth of voice packets.
Japanese Laid-Open Patent Application No. 2005-80157 (to be referred to as patent document 2) discloses a communication system for performing priority control using a bandwidth allocation management apparatus called an access point manager. FIG. 1 shows the communication system. The communication system shown in FIG. 1 includes a SIP (Session Initiation Protocol) server 1, an access point manager 3, access points 5a and 5b, and wireless terminals 7a and 7b. The SIP server 1 controls VoIP (Voice over Internet Protocol) communications based on SIP protocol. The access point manager 3 receives a request for terminal registration of the wireless terminal from the access point. In addition, the access point manager 3 sends a request for bandwidth allocation from the SIP server 1 to the access point. Each of the access points 5a and 5b deals with voice packets of the VoIP communication preferentially based on the request for bandwidth allocation from the access point manager.
In this communication system, when the wireless terminal 7a performs VoIP communications with the wireless terminal 7b based on the SIP protocol, the following procedure is carried out. When the wireless terminal 7a sends a connection request to the SIP server via the access point 5a in step 1, the SIP server 1 sends the request for bandwidth allocation to the access point manager 3 in step 3. The access point manager 3 sends the request for bandwidth allocation to the access points 5a and 5b that are an origination side and a destination side respectively in step 5, so that the access points 5a and 5b allocate bandwidth. As a result, VoIP communications from the wireless terminal 7a to the wireless terminal 7b can be performed.
In this communication system, a following phenomenon occurs when there are a plurality of SIP servers as shown in FIG. 2. It is assumed that the SIP server 1a, the access point manager 3a and the access point 5a are associated with each other, and that the SIP server 1b, the access point manager 3b and the access point 5b are associated with each other. When the wireless terminal 7a resides within a receiving range of the access point 5a, the wireless terminal 7a can perform priority controlled VoIP communication with the wireless terminal 7b according to the above-mentioned procedure. However, when the wireless terminal 7a moves to a receiving range of the access point 5b, the wireless terminal 7a sends a SIP signal to the SIP server 1a. This is because subscriber data of the wireless terminal 7a is registered in the SIP server 1a so that the wireless terminal 7a sends the SIP signal only to the SIP server 1a in which the wireless terminal 7a is registered. Therefore, the SIP server 1a sends a request for bandwidth allocation to the access point manager 3a, but, since the access point manager 3a does not manage the access point 5b, the request for bandwidth allocation ends in failure.
As mentioned above, since the wireless terminal recognizes the SIP server for sending the SIP signal, the request for bandwidth allocation ends in failure when the wireless terminal moves and accesses the previous SIP server. As a result, priority control cannot be performed.